1. Field of the Invention
This invention embodies the provision of a tailorable self-lubricating composite for use in the fabrication of bearings, bushings, and other structural components that are intended for use under dynamic loads which exceed 4,000 psi and operate at temperatures in excess of 500.degree. F. These composites must have low wear rates, low coefficients of friction, high compressive strength, and high oxidative stability in air at temperatures which range from 500.degree. F. to 600.degree. F. and above.
2. Description of the Prior Art
There are numerous, commercially available, self-lubricating composites presently in existence. However, insofar as it is known, none of the commercially available prior art self-lubricating composites are capable of withstanding both high load (in excess of 4,000 psi) and high temperature (greater than 500.degree. F.) operations for extended time periods.
The best known examples of commercially available prior art self-lubricating composites are embodied in the "Kinel" polymide based self-lubricating composites manufactured by Rhone Poulenc of Paris, France; the "Ryton" polyphenylene sulfide based self-lubricating composites manufactured by Phillips Petroleum Company or Bartlesville, Okla.; and the "Vespel" graphite filled polymide self-lubricating composite manufactured by Dupont Chemical Company of Wilmington, Delaware.
Concerning the present invention, the closest prior art, known to Applicants herein, is embodied in U.S. Pat. No. 4,075,111 for Heavy Metal Chalcogenide-Polyimide Lubricative Composites that are issued to Applicant Michael N. Gardos herein and Norman Bilow on Feb. 21, 1978. The "111" Bilow-Gardos patent teaches self-lubricating composites comprising cured acetylene-terminated polymide oligomers filled with molybdenum disulfide, or various other chalcogenides, such as tungsten disulfide, tungsten diselenide, and molybdenum diselenide, in concentrations up to 70% by weight. While the self-lubricating composites of the "111" patent exhibit high temperature stabilities, these composites are incapable of sustained operations at loads which exceed 4,000 psi.
There are many researchers striving to produce self-lubricating coposites which are capable of sustained load carrying capacities up to 172 mega pascals (MPa). References which illustrate this work include but are not limited to Perkins, C. W. "The Tribological Aspects of Carbon Fiber Reinforced Plastics", D. Mat. Report No. 173, Department of Trade and Industry, London, 1971; Giltrow, J. P., "A Synopsis of the Tribological Characteristics of Carbon Fiber Composites", Royal Aircraft Establishment Report No. 72092, May 1972; Giltrow, J. P., et al, "The Role of the Counterface in the Friction and Wear Carbon Fiber Reinforced Thermal Setting Resins", Wear, 16 359 (1970); and Brown, R. D., and Blackstone, W. R. "Evaluation of Graphite Fiber Reinforced Plastic Composites for Use in Unlubricated Sliding Bearings", ASTM Conference, Williamsburg, Virginia, March 1973.
While these prior art approaches taken by each of the above-identified researchers have proven generally satisfactory in some respects, their resultant composites have not been able to adequately withstand the high pressures and high temperatures to which they are subjected under certain high load conditions. As will become more apparent hereinafter, it is the solution to this latter problem to which the present invention is directed.